<!DOCTYPE html>

<html lang="en">
    <head>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <title>用边框凑的图形</title>

        <style type="text/css">
            .wrapper { margin: 15px auto ; }

            .first {
                width: 0 ;
                height: 0 ;
                border-top: 100px solid blue ;
                border-right: 100px solid purple ;
                border-bottom: 100px solid green ;
                border-left: 100px solid red ;
            }

            .second {
                width: 0 ;
                height: 0 ;
                border-top: 100px solid blue ;
                border-right: 100px solid purple ;
                border-bottom: 100px solid green ;
                border-left: 100px solid red ;
                border-radius: 50%/50% ;
            }

            .third {
                width: 0 ;
                height: 0 ;
                border-top: 100px solid transparent ;
                border-right: 100px solid purple ;
                border-bottom: 100px solid transparent ;
                border-left: 100px solid red ;
                border-radius: 50%/50% ;
            }

            .fourth {
                width: 0 ;
                height: 0 ;
                border-top: 100px solid transparent ;
                border-right: 50px solid transparent ;
                border-bottom: 100px solid transparent ;
                border-left: 150px solid red ;
            }

            .fifth {
                width: 0 ;
                height: 0 ;
                border-top: 100px solid transparent ;
                border-bottom: 100px solid transparent ;
                border-left: 200px double red ;
            }

        </style>
    </head>
    <body>

        <div class="wrapper first"></div>
        <div class="wrapper second"></div>
        <div class="wrapper third"></div>
        <div class="wrapper fourth"></div>
        <div class="wrapper fifth"></div>
        <div class="wrapper sixth"></div>
        
    </body>
</html>